Magnetic tachometer.



J. K. STEWART.

MAGNETIC TAUHOMETER.

- APPLIOATIOX IILED mn. 29, 1909.

Patented Apr. 18, 1911.

, To all whom "it may concern:

UNITED STATES PA TENT OFFICE.

JOHN K. STEWART, OF CHICAGO, ILLINOIS.

MAGNETIC TAOHOKETER.

Specification of Letters Patent. Patented Apr. 18, 1911- Application filed March 29, 1909. -Serial No. 486,362.

"element of low magnetic resistance interhereinafter described is mounted for rota posed in the magnetic field,-one of the three elements being rotated and-the second having an indicating device, as an index finbeing mounted for oscillation ger, and against -a yielding resistance or biasing means, the deflection of the index. finger being caused by the magnetic drag of the rotating element upon the oscillating element.

It consists of the features of construction and their combinations shown and'described as set forth'in the claims.

In the drawings :-Fi'gure 1 is a face view of a tachometer embodying this invention, a portion of the dial plate andarmature disk being broken away to disclose the interior elements. Fig. 2 is an axial section of the same. Fig. 3 is an inverted plan view of the magnets and carrierand adjusting device, the latter being partly broken away.

In the structure shown embodying this invention, there is employedsan inclosing case, A, substantially cylindrical in form, open'at one end, at which there is mounted a dial plate, B, protected by a glass, C. At the center of the case, rigid with the back or bottom disk or web, 1 thereof, there is erected and preferably formed integrally with said web a post, 2, upon which themagnet tion. Preferably, the post is constructed to rovide ball bearings for the magnet, and or that purpose is reduced in diameter at 2 its upper part, reduction commencing with an inclined shoulder, 3, which'constitutes the blower ball seat of the ball bearing indicated by the balls, D, and the 0st may be divided transversely above this all seat, the upper member, 6, being made with a long ienon or spindle, 6, for connecting it with thelower member of the post, the latter being axially apertured to receive said tenon or spindle,

this invention is to provide I vary the leverage by which the and said upper member being at its upper end expanded to form a cone, 7, corresponding to the sloping shoulder, 3, for the upper ball bearin Suitable hall recesses are formed by annular rabbets, 5, in the magnet element. The magnet element comprises the body or magntcarrier, E, which terminates at the lower end inan interior beveled gear rim, 4, and

is axially apertured' for passing on to the reduced upper portion or upper member, ,6,

of the post, 2, and. provided with annular rabbcts, ,5, to form the ball recesses above mentioned. The spindle, 6", of said upper member, 6, is designed to fit snugly in the axial apertureof the lower member, 2 of the post, so as to preservethe upper member in perfect axial alinement with the lower bearing of the magnet element. In the magnet body or carrier, E, there are mounted a plurality,as illustrated, four,.-of horse-shoe magnets, E said bod being recessed to receive these magnets w ich fit snugly in their respective recesses which they enter radially and in which they are furtherpositioned longitudinally with respect to the magnet body by radial guide'studs, E, which are I rigid with said body or carrier and on to which the magnets pass in entering the radial recesses provided for them in the carrier.

Below the magnet seats or recesses the carrier, E, is reduced in diameter to form a cylindrical hub upon which there is mounted a sleeved gear, J, whose sleeve portion, J ,fits upon said reduced cylindrical hub of the carrier and is stopped longitudinally thereon by studs, j, j, projecting from the hub and taking into circumferentially extending slots, in the sleeve, one of said studs, i being a screw having a slotted head, 7', for binding on the sleeve to secure the device in adjustment. In the gear itself,-that is, the I portion which constitutes the annular flange about the sleeve,there are formed four slots, 3', of which one is shown in Fig. 3 slightly and similarly eccentric with respect to the sleeve, and each of themagnets is provided with a downwardly pro ecting stud, e, taking into the corresponding slot, 7', so that the rotation of the gear causes the magnets to be moved slightly radially with respect to the carrier. This adjustment is provided for the purpose of calibr tion to, rdagnetio drag operates upon the oscillating disk for actuating the index finger hereinafter described.

For efiecting the adjustment in the original assembling and calibration of the instrument, the case, A, has a lateral aperture, A whose margin affords a bearing for a key, M, which is adapted to beiin'serted therethrough, said key having a tubular stem whose cavity, 771-, fits the head of the screw, j said head thereby becomin a second bearing for the key. At suitab e position in its length for meshing with the gear flange, J, when the key is centered on the screw, j there is formed on the key a pin-- ion, M by which the gear may be rotated by rotatingthe key. The axial aperture of the key admits a small screw driver, N,

which may be inserted therethrough for engaging the head of the screw, y' to loosen the screw before rotating the key and for tightening it after the adjustment is eflected. It will be understood that the key and screw driver are not permanently associated with the case, but are introduced thereinto only for the purpose of adjustment described. It will be understood that the gear flange, J, need not be toothed except for a segment corresponding to the range of one of the cam slots, and it is so illustrated.

axially bored at 11, from its upper end, and receives at the bottom of said bore a step bearing, 12, for the spindle, 13,,of a disk, F, made of material havinglow ma etic resistance, such as aluminum. This isk is positioned so as to be spaced a very short distance from the upper poles of the magnet. The case, A, is interiorly rabbeted to form a shoulder, 15, and is also provided with posts 15, positioning and supporting an armature disk, G, which also serves to complete the inclosure ofthe chamber in which the magnet and the disk, F, are located. The spindle, '13, of the disk, beside its step hearing at 12, may be provided with a sec- =ond steadying bearing, 16, at the center of the disk, G, which is penetrated by the spindle and carries at its upper end an index finger, H. Above the armature disk,. G, there is located a helical spring, S, connected at its inner end with the spindle and at its outer end with a stud, 17, projecting latera'lly' from a wormgear, 18, mounted upon the hub,,.g, of the disk, G, for rotation thereon, and meshing with a worm, T, on a horizontal shaft, t, which is journaled in the case and accessible through an aperture, a, therein for'rotating the worm to thereby rotate the worm gear to adjust theposition of the outer end of the helical spring to vary its tension and the yielding resistance whichit opposes to the drag of the magnet upon the disk, F. i

The two means shown for inodifving the The upper member, 6, of the post, 2, is

action of the magnet on the disk, F, are each desirable, the ad ustment of the magnets radially in the carrier beingdesigned to be resorted to in the construction of the instrument for calibrating, and the adjustment of the tension of the spring being rethe shaft, K, having ball bearings at 20, 20,

insaid journal bearing element. -This shaft, K, at its inner end within the case terminates in a beveled pinion, 22 whichmeshes with the internal beveled gear, 4, formed at the lower end of the magnet carrier, as described for communicating rotary motion to said carrier. to be connected in any convenient manner with the shaft whose rotary speed is to be indicated by the instrument, andit is shown flattened and aperture'd at its end, 21, to in dicate the intention and adaptation for such connection.

Iclaiinz- 1. In a magnetic tachometer, in combination with a case, a post within the casefa permanent magnet element and an armature,

one mounted for rotation on thepost and the other supported fixedly on the case, the magnet element comprising a carrier and The shaft," K, is designed amagnet movable radially on the carrier;

a low resistance disk positioned between the magnet element and the armature, having a spindle provided with a step bearing within the. post and extending through the fixed element; a spring which operates to hold the disk yieldingly against rotation away from a predeterminedposition;' an indicator carried by the spindle, and means for adjusting the magnetradially on the carrier.

2. In a magnetic tachometer, in combina tion with a case, a post within the case; a permanent magnet element and an armature, one mounted for rotation on the post and the other supported fixedly on the case, the magnet element comprising a carrier, and a plurality of horseshoe magnets mounted for movement radially on the carrier; a low resistance disk positioned between the magnet element and the armature,' having a spindle provided with a step bearing within the post and extending through the fixed element; a springwhich operates to hold the disk yieldingly against rotation away from a predetermined position; an indicator carried by the spindle, and means for adjusting the horse-shoe magnets radially on the carrier.

3; In a magnetic tachometer, in combination with a permanentmagnet element and an armature mounted for relative. rotation, 1

a low resistance disk positioned between the magnet and the armature, mounted for oscillation about the axis of rotation of the rotating element; means for yieldingly resisting such oscillation, the magnet being mounted for movement radially with respect .to the axis of rotation, and means for adjust-ing it radially.

i an armature, a support for both said elements with respect to which one is mounted for rotation and the other is supported fixedly; a lowresistance disk positioned between the magnet and .thearmature, mounted for'oscillation about the axis of rotation;

means which yieldingly resists its movement away from a 'pre-determined position, the magnet element comprisinga carrier and a magnet mounted for radial movement thereon, and means for adjustingtthe magnet radially on the-carrier. 6. In a magnetic tachometer, in combination with a permanent magnet element and an armature, asupport for both said elements with respect to which one is mounted for rotation about an axis and the other is supported fixedly; a low resistance disk positioned between the magnet and the armature, mounted for oscillation about the axis of rotation .of the rotatin element; means for yieldingly resisting t e movement of said oscillating element away from a pre' determined position, the magnet element comprlsing a carrier and a plurality of magnets disposed about the axis of rotation, movable on the carrier radially 'with respect to said axis, and means for adjusting the magnets with respect to said axis.

7. lna magnetic tachometer, in combination with a case, a permanent magnet element mounted in the case for rotation; an armature supported'fixedly .on the case; a low resistance disk positioned between the magnet and the, armature, mounted for oscillationabout the axis of rotation of the magnet; means operating to hold the disk yleldlng'ly against movement in the plane of oscillation away from a pre-determiired, position, the magnet element comprising a (-HI'IIPJ', and a plurality ofmagnets disposed through the fixed element; a worm for adjustment toward and from the axis; a cam plate mounted onthe carrier for move- -ment relatively, thereto about the axis and means by whichit engages the magnets for moving them'on the carrier by rotation of the plate, and means for rotating the plate. 8. In a magnetic tachometer, 1n combination with a case, a permanent magnet' element mounted in the case for rotation; an armature supported fixedly on the case; a low resistance disk positioned between the magnet and the armature mounted for oscillation about the axis of'rotation of the magnet; means operating to hold the disk yield-- ingl against movement in the plane of osci lation away from a pre-determinedposition, the magnet element comprising a carrier and magnets disposed thereon about the axis of rotation mounted for adjustment toward and from the axis; a cam plate mounted on the carrier for rotatlon relatively thereto and means by which it engages the magnets formoving them toward and from the axis by rotation of the cam plate, said cam plate being provided with means for engagement at its periphery to adjust it about said axis, the case having an a erture through which access may be obtalned to said periphery for adjusting the cam plate. f

9. In a magnetic tachometer, in combine-- tion with a case, a permanent magnet elel ment mounted inthe case for rotat-longan armature supported fixedly on. the case; a

low resistance disk positioned between the magnet and the armature mounted for oscillation about the axis of rotation of the ma net; means operating to hold the disk yiel ingl against movement in the plane of osci lation away from'a pie-determined position, the magnet element comprising a carrier and magnets disposed thereon about the axis of rotation mounted for adjustmenttoward and from the axis; a cam device mounted on the carrier for rotation relatively thereto and means bywhich it engages the-magnets for moving them toward an from the axis of rotation of the cam device; a binding screw for securing the cam device in adjusted position about said axis,

thecam device having a gear se ment; the case having an aperture which a fi' ords hearing for a key to be inserted therethrough for engagement with the clamping screw, and means to engage the gear segment to rotate the cam device.

10. In a magnetic tachometer, in combination with a case, an interior post; a perma' nent magnet element and an armature, one mounted for rotation on the post and the other supported fixedly on the case; a low resistance disk positioned between the magnet element and the armature, havin a spindle stepped in the post and exten mg ear thereon about the axis of rotation,- mounted mounted for rotationon the armature it, out

the axis" of the spindle; a spring connected atjone end to said worm gear and at the other .end to the spindle for holding the. disk yieldingly against rotation. from pre-determined position; a worm engaging said worm gear, and means for rotating the Worm. a.

Q11. In combination with ,a permanent magnet element and anarmature element mounted for relative r'otatiori;" one. of said elements having peripheral portions move able with respeetto the remainder of said element toward and from the axis of rota; hon; means for so moving the same;".a 10W- esepse resistance disk positioned between the magnet and the armature mounted for rotation about the axis of the rotating element, and a spring for yieldingly resisting such-r0- tation. a

In testimony whereof, I have hereunto set my hand, in the presence of two witnesses, at Chicago, Illinois, this 25th day of March, A. D. 1909.

JOHN K. STEWART.

In the presence ofr M. GERTR DE Amt,- J ULIA S. Annorr. 

